OBJECTIVES: To learn how both "early" and "late" functions of polyoma virus are expressed and regulated during the lytic cycle. To do this we will prepare poly(A) containing mRNAs from infected cells at different times post infection and translate these mRNAs in a variety of cell free systems. Viral specific mRNAs will be isolated by hybridization to covalently immobilized viral DNA. Preparations of viral specific mRNAs will be fractionated according to size to determine the number of different species. Size purified mRNAs will be translated to determine which viral proteins they code for. We will also pay attention to poly(A) deficient mRNAs, since late in infection there is at least one virus specific mRNA of this sort. The amounts of the various viral mRNAs late in infection will be quantitated to determine how the transcription of the late region is controlled. We will investigate the transcription and translation patterns in a number of "late" temperature sensitive mutants of polyoma to see whether we can find any evidence for regulation by viral gene products. To determine whether the synthesis of polyoma DNA occurs by a discontinuous mechanism on one or both sides of the growing fork.